server - (optional); if specified runs Sage on a
remote machine with address. You must have ssh keys setup so you
can login to the remote machine by typing “ssh remote_machine” and
no password, call _install_hints_ssh() for hints on how to do
that.

The version of Sage should be the same as on the local machine,
since pickling is used to move data between the two Sage process.

EXAMPLES: We create an interface to a copy of Sage. This copy of
Sage runs as an external process with its own memory space, etc.